This invention relates in general to respirators and in particular to a new and useful respirator for use in pressure chambers.
The use of pressure chambers for therapeutic purposes or the necessity of medical care in diver pressure chambers requires medical instruments and thus also respirators which can be used under pressure chamber conditions. The fully pneumatic respirators used here depend on the ambient pressure. The ventilation parameters set at atmospheric pressure, like respiratory output (AMV) and the breathing rate vary with the chamber pressure. During compression and decompression, constant readjustment is necessary.
A known respirator, particularly for infants, switches the inspiration and expiration phase by controlling the expiration valve from a time-control system composed of pneumatic parts. The pressure of the ventilating gas fed to the respirator through a filter, is reduced in a pressure reducer to the operating pressure. It serves to supply the patient and effects the operation of the time-control system. The ventilating air is fed to the patient over a flow valve and subsequently released into the atmosphere through an expiration valve controlled by the time-control system. The time-control system is composed of pneumatic logic elements which are connected in the form of two chains and are joined at their ends to form a bistable switch. Each chain determines the duration of a breathing phase to this end, a volume is provided in each chain which together with a precision regulating valve forms and RC-sector. After charging the respective volume to a switching pressure of 80% of the operating pressure, the other breathing phase is started by switching to the other chain, and at the same time the pressure is released in the charged volume.
Such a respirator is not suitable for use in pressure chambers. When the chamber pressure rises, the supply of ventilating gas is no longer sufficient. The flow valve must be constantly readjusted. Besides, higher chamber pressures cause a faster switching of the control for the breathing rate. Here, too, constant readjustment is necessary. (DE-OS No. 28 01 546).